Solid detergent composition

ABSTRACT

A continuous process for casting comprising the steps of i. filling a continuous tube of flexible material with a melt of the castable composition, where the tube acts as a sleeve to the composition, such that a desired cross section area of the filled sleeve is obtained that is independent of its perimeter ii. solidifying and simultaneously shaping the said melt by cooling the said filled sleeve in or on a suitable mould.

TECHNICAL FIELD

The present invention relates to a process for continuous casting of asolid detergent composition.

BACKGROUND AND PRIOR ART

Soap or non-soap detergent articles are traditionally produced either byextrusion or by casting routes.

The processing/finishing of a detergent article via the extrusion routeoften involves various operations such as homogenisation, shear working,and forming into a suitable shape. A plodder or extruder is usuallyemployed to take care of part of the shaping operation. The product fromthe extruder may be cut into logs and/or billets which are subsequentlystamped and shaped into tablets or bars. The extrusion of soap ordetergent mass is a continuous operation.

The casting route for detergent bars is traditionally employed forexample for producing highly transparent soaps. The most widely employedtechnology involves many manufacturing operations such as casting ofmolten soap into logs of desired cross section in moulds, cooling, logejection, log maturation, billeting, chamfering, billet maturation andstamping to produce individual transparent soap tablets or bars.

Casting allows for high formulation flexibility, for instance highlevels of liquid benefit agents and water can be incorporated into thecomposition. Highly transparent bars can be processed by casting.

However, conventional casting is a batch/semi-continuous operation andtherefore is highly labour/capital intensive as compared to extrusionwhich is a continuous operation. Continuous casting is employed forrapid setting materials such as steel and glass under continuous“drawing” conditions. However such a process can not be employed for nonquick setting materials such as soaps and detergents. Thus it would beuseful to make the casting of non-quick setting materials a continuousoperation and less labour/capital intensive.

EP 321,179 (Unilever), discloses a method of casting soap or detergentwherein liquid or semi-liquid soap is filled into a pack made offlexible film, such that the material occupies the whole of the pack.The pack is then tightly sealed to exclude air and the material isallowed to set in the pack to obtain cast in pack tablets. This processwill help in producing a continuous string of packed soap sachets. Theability to manipulate shape of the tablet in such a process is limited.Minor shape manipulations are achieved by pressurising the pack that isessentially made of heat or pressure extendable film and in general theshape obtained is in the form of a cushion. Such internal pressure canbe developed by externally compressing the sealed sachet. The process,although referred to as a continuous method of casting, requires sealingand pressurising of individual sachets, and thus would significantlyslow down the throughput rates. In the absence of the heat extendable orshrinkable polymers there would be formation of wrinkles on the casttablets.

It has now been possible to have a simple, economical, continuousprocess for casting of non-quick setting materials, at high through putrates. It is further possible to obtain a desired shape of tablet, freeof wrinkles and air cavities, without having to use heat extendablepolymers, and without pressurising the filled liquid. In the process ofthe invention, the melt of the castable composition is filled into atube made of flexible material where the tube acts as a sleeve to thecomposition, such that desired cross section area of the filled sleeveis obtained that is independent of the perimeter of the sleeve. Thefilled sleeve is then shaped during cooling and solidification. Theprocess produces cast-in-sleeve logs that can be cut intobillets/tablets and optionally flow wrapped.

The tube made of the flexible material does not necessarily have acircular cross section. The sleeve provides a means for pulling,conveying and shaping of the liquid. The melt of the composition isfilled into the tube, acting as a sleeve for the composition, with acontrol on cross section area of the filled sleeve which is independentof the perimeter of the sleeve. This fact in turn, can be exploited toobtain the desired shape during cooling and solidification. One of themeans for achieving desired cross section area of the filled sleeveindependent of the perimeter is to provide a guide that constrains thesleeve during filling. The other means could be to fill to less than100% of the internal volume of a substantially air free tube. Internalpressure is not required for achieving desired shapes of tablets. Theincreased throughput is achieved by avoiding the sealing of theindividual sachets and producing continuously shaped cast-in-sleeve logsthereby simulating the extrusion process. The shaping is achieved byplacing the sleeve filled with the liquid composition on a suitablerigid mould during cooling and solidification. The sleeve filled withthe liquid composition is pulled either horizontally or vertically andcooled to bring about solidification.

The above described continuous casting process is suitable formanufacturing any non quick setting materials such as soaps, detergenttablets, deodorants, confectioneries, etc.

OBJECTS OF THE INVENTION

Thus, it is an object of the invention to provide a simple, economical,continuous process for in-sleeve-casting of non quick-setting materialswhereby the shape of the cast product is controlled.

DESCRIPTION OF THE INVENTION

According to one aspect of the present invention there is provided acontinuous process for casting comprising the steps of:

i. filling a continuous tube of flexible material, optionally formedonline with a melt of the castable composition, where the tube acts as asleeve to the composition, such that the desired cross section area ofthe filled sleeve is obtained that is independent of its perimeter; and

ii. solidifying and simultaneously shaping the said melt by cooling thesaid filled sleeve in or on a suitable mould.

It is particularly preferred that the desired cross section area of thefilled sleeve independent of the perimeter of the filled sleeve isachieved by providing a guide that constrains the sleeve during fillingor by filling to less than 100% of the internal volume of asubstantially air free tube.

According to a preferred aspect of the present invention there isprovided a continuous process for casting comprising the steps of:

i. filling a continuous tube of a flexible material, optionally formedonline, with a melt of the castable composition, where the tube acts asa sleeve to the composition, and simultaneously conveying through across section constraining guide to achieve desired cross-section areaof the filled sleeve that is independent of its perimeter

ii. solidifying and simultaneously shaping the said melt by cooling thesaid filled sleeve in/on a suitable mould

iii. cutting the said continuously formed shaped and solidified castcomposition into logs/billets/tablets.

iv. optionally flow wrapping the said logs/billets/tablets

According to a more preferred aspect of the present invention there isprovided a continuous process for casting comprising the steps of:

(i) filling to less than 100% of the internal volume of a substantiallyair free continuous tube of a flexible material, optionally formedonline, the said tube sealed at the bottom end, with a melt of thecastable composition and sealing the filling end to obtain acast-in-sleeve melt

(ii) solidifying and simultaneously shaping by cooling the said melt toobtain cast-in-sleeve log of the composition

(iii) optionally cutting the said shaped and solidified cast-in-sleevelog into billets/tablets

(iv) optionally flow wrapping the said logs/billets/tablets.

According to a most preferred aspect of the present invention there isprovided a continuous process for casting comprising the steps of:

(i) filling a continuous tube of flexible material formed online andsealed at the bottom end, with a melt of the castable composition, wherethe tube acts as a sleeve to the composition, and simultaneouslyconveying through a cross section constraining guide to achieve desiredarea of cross section of the filled sleeve that is independent of theperimeter

(ii) sealing the filling end of the filled tubular sleeve without airentrapment to obtain a cast-in-sleeve melt

(iii) solidifying and simultaneously shaping the said melt by coolingthe said filled sleeve on a suitable mould to obtain a cast-in-sleevelog

(iv) cutting the said shaped and solidified cast composition intobillets/tablets.

(v) optionally flow wrapping the said logs/billets/tablets

The different products that can be cast using the above process are forexample soaps, detergents, deodorants or confectioneries. However, theprocess is particularly preferred for home and personal carecompositions such as soap and detergent bars or tablets.

The cast-in-sleeve detergent tablet can be transparent ornon-transparent and formed from any suitable formulation known in theart. The composition can comprise only soap as the active or can be incombination with non-soap detergent actives. The billets or tablets ofthe detergent composition can optionally be dehydrated.

The particularly preferred detergent composition comprises

i. 10-60% saturated fatty acid soap

ii. 0-40% non-soap detergent active

iii. 20-80% water

iv. optionally salting in electrolytes, solubilizers such as polyols,benefit agents, etc.

DETAILED DESCRIPTION OF THE INVENTION

The essential feature of the invention is that the through put of thecasting process can be significantly enhanced and desired shapes oftablets can be obtained by filling a melt of the composition into a tubeof flexible material that acts as a sleeve to the composition,optionally formed online, such that desired cross section area of thefilled sleeve is achieved independent of the perimeter of the sleeve.The filled sleeve is shaped during cooling and solidification to obtaincast-in-sleeve log. The increased throughput is achieved by avoidingsealing of the individual sachets and producing continuously shapedcast-in-sleeve logs thereby simulating the extrusion process. It ispossible to use any flexible material without having to use specialpolymers such as heat extendable or shrinkable or heat sealable polymersto obtain tablets with desired shapes. The shaping is achieved byplacing the tubular sleeve filled with the liquid in or on a suitablerigid mould during cooling and solidification.

The nature of the invention, its objects and advantages will be moreapparent from the following detailed description and these arenon-limiting details of the different aspects of the invention.

The tube:

The tube used in the casting process can be either preformed or formedonline from a suitable flexible material. The tube acts as a sleeve tothe composition. The tube is preferably formed online. In a preferredmethod of forming the tube online, a suitable flexible material isenveloped around a rigid forming unit and sealed vertically to form thetube. The tube need not necessarily be of circular cross section. Thetube provides a means for pulling, conveying and shaping of thecomposition.

It is preferred that a tube substantially free of air is obtained priorto filling the melt of the castable composition, if guide is not used toachieve desired cross section of the filled sleeve independent ofperimeter of the sleeve. One of the ways of obtaining a tubesubstantially free of air is to minimise or avoid air leakage into thetube during its formation from the flexible material. In one of thepreferred means of achieving desired cross section area of the filledsleeve independent of the perimeter of the sleeve, the melt of thecastable composition is filled to less than 100% of the internal volumeof a tube substantially free of air and then sealed to obtain acast-in-sleeve melt. The tubular sleeve containing melt of thecomposition is then shaped during cooling and solidification.

The tube is made from a flexible material such as polymer, rubber,paper, fabric, etc. The flexible material should be chosen such that themelt of the composition being filled into the tube should not leak underhydrostatic pressure. Polymers are especially suitable to make the tube.It is not essential that the polymer be heat sealable, heat shrinkableor heat extendable. It is also possible to use laminated films. Polymerssuitable for making the tube include poly(vinyl chloride), nylon,polyester, polystyrene, cellulosic polymers and polyethylene. Lessexpensive materials like polyethylene and paper coated with polyethyleneare especially preferred.

Guide:

One of the other means of achieving desired cross section area of filledsleeve independent of the perimeter of the sleeve is to provide a guidethat constrains the tube during filling. Thus, the volume occupied bythe composition per unit length of the tube is lower when the guidingmechanism is in place. In the process the guide must be provided untilthe composition is cooled to obtain the desired three dimensional shapewhich otherwise will change under hydrostatic pressure.

As an alternative it is possible to seal the sleeve by sealing throughthe liquid while the sleeve is still guided to obtain a log ofcast-in-sleeve melt. The guide also ensures that the air bubbles stayout of the log of the cast-in-sleeve melt at the time of top sealing. Inthis case it is not essential to maintain the guide until shaping but itis essential to have the composition in the melt form to give it thedesired shape. If the composition solidifies before shaping it ispossible to remelt and then shape the same.

Without being limited by the same, the guiding means is provided byconstraining the filled tubular sleeve between two movable rigidsurfaces prior to top sealing. Examples of such surfaces include flatplates, rods, curved plates etc.

The Composition:

The different products that can be cast by using the above process maybe a soap, detergent, deodorant or confectioneries. However, the processis particularly preferred for home and personal care compositions suchas soap and detergent bars.

The Detergent Composition:

Any castable detergent composition disclosed in prior art is suitablefor the process of the invention. The particularly preferred compositioncomprises:

i. 10-60% saturated fatty acid soap

ii. 0-40% detergent active

iii. 20-60% water

iv. optionally salting-in electrolytes, polyols, benefits 10 agents etc.

Saturated Fatty Acid Soap:

The saturated fatty acid soap is preferably selected from one or moresalts of C₆-C₂₄ fatty acids. The soap employed may for example be asodium, potassium, magnesium, aluminium, calcium or lithium salt ofsaturated fatty acids. It is especially preferred to have soap obtainedas sodium or potassium salt of saturated fatty acid.

The saturated fatty acid soap in the composition is preferably 10-60% byweight of the composition, most preferred from 15 to 40% by weight.

Detergent Active:

The compositions according to the invention optionally comprisedetergent actives. The detergent active can be non-soap detergentactives or the salts of unsaturated fatty acids. Non soap detergentactives are suitably selected from anionic, non-ionic, cationic,amphoteric or zwitterionic surfactants or their mixtures. The detergentactive is suitably used in an amount of from 0 to 40% by weight of thecomposition, most preferred 5 to 35% by weight of the composition.

Examples of suitable detergent active species are given in the followingwell-known textbooks: (i) “Surface Active Agents”, Volume I by Schwartzand Perry, (ii) “Surface Active Agents and Detergents”, Volume II bySchwartz, Perry and Berch, (iii) “Handbook of Surfactants”, M. R.Porter, Chapman and Hall, New York, 1991.

Salting-In Electrolytes:

Salting-in electrolytes for use in the composition are selected fromthose listed in the ‘Hofmeister’ or ‘Lyotropic’ series. The salting-inelectrolytes are generally those wherein the lyotropic number for theanion of the electrolyte is >10. Some examples of anions with lyotropicnumber >10 are NO₂ ⁻, ClO₃ ⁻, Br⁻, NO₃ ⁻, ClO₄ ⁻, I⁻, CNS⁻, C₆H₅SO₃—,C₆H₄CH₃SO₃ ⁻ and Cr₂O₇ ²⁻. The preferred examples of salting-inelectrolytes for use in compositions according to the present inventionare alkali metal salts of the above mentioned anions. The most preferredexamples of the salting-in electrolytes for use in compositionsaccording to the present invention are sodium toluene sulphonate, sodiumcumene sulphonate and sodium xylene sulphonate. Further examples ofsalting-in electrolytes may be selected form those described in (i)Collins, K. D.; Washabaugh, M. W. Quart. Rev. Biophys., 1985, 18, 323;(ii) Schuster. P, Zundel. G and Sandorfy. C, 1976, ‘The Hydrogen Bond’,Recent developments in theory and experiments, Vol. III, North-HollandPublishing Co. Amsterdam, New York, Oxford.

Liquid Benefit Agents:

According to a preferred aspect of the invention, liquid skin benefitmaterials such as moisturisers, emollients, sunscreens, anti ageingcompounds are incorporated in the composition. Examples of moisturisersand humectants include polyols, glycerol, cetyl alcohol, carbopol 934,ethoxylated castor oil, paraffin oils, lanolin and its derivatives.Silicone compounds such as silicone surfactants like DC3225C (DowCorning) and/or silicone emollients, silicone oil (DC-200 Ex-DowCorning) may also be included. Sun-screens such as 4-tertiarybutyl-4′-ethoxy dibenzoylmethane (available under the trade name PARSOL1789 from Givaudan) and/or 2-ethyl hexyl methoxy cinnamate (availableunder the trade name PARSOL MCX from Givaudan) or other UV-A and UV-Bsun-screens.

Solubilisers:

Solubilisers suitable for use in the detergent composition includemonohydric and polyhydric alcohols such as propylene glycol, sorbitol,glycerine etc.

Optional Ingredients:

Other optional ingredients such as hair conditioning agents, fillers,colour, perfume, opacifier, preservatives, one or more water insolubleparticulate materials such as talc, kaolin, polysaccharides and otherconventional ingredients may be incorporated in the composition.

Cooling and Shaping of the Composition:

The melt may have any suitable temperature, for example up to 120° C.,most preferred from 40° C. to 90° C. The melt of the composition in thetubular sleeve (cast-in-sleeve composition) is passed through a coolingtunnel to bring about solidification. The product is simultaneouslyshaped in the cooling tunnel. The shaping is achieved by providing aconveyor belt in the cooling tunnel, said belt being flat or curved,thus imparting the required shape to the solidified composition. Forexample, a flat conveyor belt can be used to obtain a flat bottom,convex top shaped cast-in-sleeve product.

It is also possible to pressurise the tubular sleeve filled with themelt of the composition between two plates to obtain a desired shape.

Another means of achieving the desired shape is to place the tubularsleeve filled with the melt of the composition in or on a suitable mouldwhich in turn is placed on the conveyor belt of the cooling tunnel.Lettering or decorative motifs can be provided during shaping in thecooling tunnel.

The solidified and shaped composition so obtained is then cut to obtaincast-in-sleeve logs or billets or tablets. Logs so obtained can befurther cut into billets or tablets. Optionally the logs or billets ortablets can be flow wrapped.

The nature of the invention, its objects and advantages will be moreapparent from the ensuing description made with relation to non-limitingexemplary examples of the above identified various aspects of theinvention.

EXAMPLES Example 1

The Detergent Composition

A mixture containing fatty acid soap, non-soap detergent, salting-inelectrolyte, and water as described in Table 1 was mixed in a two litrecapacity round bottom flask. The batch temperature was raised to 80° C.The batch temperature was maintained at 80° C. so that a clear pourableliquid was obtained. TABLE 1 Wt % of the Component Composition Sodiumstearate  20 Sodium lauryl ether sulphate  15 Sodium toluene sulphonate 10 Water  55 Total 100

Example 2

Continuous Casting Process to obtain a Cast-In-Sleeve Product withoutSealing the Sleeve

FIG. 1 shows a schematic representation of the continuous castingprocess. The flexible film (FF) is continuously formed in the formingand filling machine (FFM) to obtain the tube. Simultaneously the melt ofthe detergent composition (DC) is filled into the said tube whileguiding the tube by a guiding means (G). The melt of the detergentcomposition in the sleeve is then solidified and simultaneously shapedby passing through the cooling tunnel (CT) provided with a flat conveyorbelt. The continuously formed, solidified and shaped detergentcomposition (SS-DC) is then cut into billets and flow wrapped using thecut and wrap machine (CWM). The flow wrapped tablets (FWT) are thencartoned. The detergent tablet had a flat bottom and a convex top thathas advantages of: (i) convenient to hold in hand and (ii) easy to applyon body or onto fabric.

Example 3

Demonstration of the Need for the Guide for Obtaining Desired Shapes

i. Casting without the Guide:

A pre-formed tube made from 80 micron thick polyethylene with 19 Cmperimeter and 80 Cm length was filled with the melt of the detergentcomposition as described in Example 1 up to a height of 70 Cm and sealedthrough the liquid at a length of 65 Cm. Two such cast-in-sleeve logswere made and one of the logs was placed on a flat surface (Example 3a)and the other on a mould with a concave surface with radius of curvature6 Cm (Example 3b), cooled to bring about solidification. The log was cutinto 10 Cm length tablets.

ii. Casting with a Guide:

A pre-formed tubular sleeve made from 80 micron thick polyethylene with19 Cm perimeter and 80 Cm length was placed in a guide made up of twoparallel flat acrylic sheets of width 8 Cm, length of 60 Cm and with aspacing of 4.5 Cm between them. The sleeve was filled with the melt ofthe detergent composition as described in Example 1 up to a height on 70Cm and sealed through the liquid at a length of 65 Cm. Two suchcast-in-sleeve logs were made and one of the logs was placed on a flatsurface (Example 3c) and the other on a mould with a concave surfacewith radius of curvature 6 Cm (Example 3d), cooled to bring aboutsolidification. The log was cut into 10 Cm length tablets.

The details of the shape of the tablets obtained are presented in Table2. TABLE 2 Examples Shape of the tablet Example 3a Cylinder with acircular cross section Example 3b Cylinder with a circular cross sectionExample 3c Substantially flat bottomed with a convex dome Example 3dCylinder with an elliptical cross section.

The data presented show that when the guide is used during casting theshape of the tablet can be controlled and the tablets obtained would befree of wrinkles.

1. A continuous process for casting soaps, detergents, deodorants orconfectionaries, comprising the steps of: i. filling a continuous tubeof flexible material with a melt of the castable composition, where thetube acts as a sleeve to the composition, such that a desired crosssection area of the filled sleeve is obtained that is independent of itsperimeter ii. solidifying and simultaneously shaping the said melt bycooling the said filled sleeve in or on a suitable mould, and whereinthe desired cross section area is achieved by a guide that constrainsthe sleeve during filling to less than 100% of the internal volume of asubstantially air-free tube.
 2. A continuous process for castingcomprising the steps of: i. filling a continuous tube of a flexiblematerial, optionally formed online, with a melt of the castablecomposition,.where the tube acts as a sleeve to the composition, andsimultaneously conveying through a cross section constraining guide toachieve desired cross-section area of the filled sleeve that isindependent of its perimeter ii. solidifying and simultaneously shapingthe said melt by cooling the said filled sleeve in or on a suitablemould iii. cutting the said continuously formed shaped and solidifiedcast composition into logs or billets or tablets.
 3. A continuousprocess for casting comprising the steps of: i. filling a continuoustube of flexible material formed online and sealed at the bottom end,with a melt of the castable composition, where the tube acts as a sleeveto the composition, and simultaneously conveying through a cross sectionconstraining guide to achieve desired area of cross section of thefilled sleeve that is independent of the perimeter ii. sealing thefilling end of the filled tubular sleeve without air entrapment toobtain a cast-in-sleeve melt iii. solidifying and simultaneously shapingthe said melt by cooling the said filled sleeve on a suitable mould toobtain a cast-in-sleeve log iv. cutting the said shaped and solidifiedcast composition into billets or tablets.
 4. Process according to claim1 wherein the detergent has a composition comprising: i. 10-60%saturated fatty acid soap ii. 0-40% non-soap detergent active iii.20-80% water